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Bread Crumbs

Yu Zhang, an associate professor of biomaterials and biomimetics at the NYU College of Dentistry, has been awarded a five-year, $1.9 million grant from the National Institute of Dental and Craniofacial Research (NIDCR), National Institutes of Health (NIH), to develop and test a prototype glass-zirconia composite dental crown.

The award enables Zhang to advance earlier research on a glass-zirconia composite formulation intended to serve as an alternative to porcelain-veneered zirconia designs. Although porcelain-veneered zirconia crowns and bridges are more aesthetically pleasing than those made from metal-ceramics, an estimated 10 percent of porcelain-veneered zirconia restorations develop fractures within the first three years.

Zhang formulated the initial prototype glass-zirconia composite material with funding from the NIH and the National Science Foundation, which awarded him more than $1.4 million in 2007 and 2008, respectively. This research showed that the composite has significantly higher load-bearing capacity than porcelain-veneered zirconia formulations.

In the newly funded NIDCR/NIH study, Zhang is using a mouth motion simulator—a machine that simulates chewing and grinding—to compare the fracture-resistance of eight glass-zirconia and eight all-zirconia crowns. Each crown will endure two months and 1.25 million chewing cycles in the simulator—which is equivalent to three meals a day over a five-year period.&nbsp;

“A composite crown with glass-rich surfaces will be less susceptible to top-to-bottom fractures from direct contact with hard food as well as to ruptures that occur when the bottom of the restoration buckles under pressure,” explains Zhang.

A glass-ceramic composite restoration offers aesthetics comparable to a porcelain-veneered zirconia version, but since it is thinner, a smaller amount of healthy tooth structure needs to be removed to make room for it. If the glass-ceramic composite crown proves more durable than the all-ceramic variant, Zhang plans to conduct a subsequent study examining the safety and efficacy of glass-ceramic crowns in human subjects.

Zhang’s co-investigators include Van P. Thompson, professor and chair of the Department of Biomaterials and Biomimetics, and Melvin Janal, adjunct associate professor of epidemiology and health promotion, both at the NYU College of Dentistry; Brian R. Lawn, an NIST Senior Fellow; and Herzl Chai, professor of mechanical engineering at Tel Aviv University.